Cathode structure



Aug. 17, 1948. SPENCER 2,447,038

CATHODE STRUCTURE Filed. Oct. 31, 1945 bVVE/VTO/f PERCY L. -5Ff/V0E/f Patented Aug. 17, 1948 CATHODE STRUCTURE Percy L. Spencer, West Newton, Mass., assignor to Raytheon Manufacturing Company, Newton,

Mass, a corporation of Delaware Application October 31, 1945, Serial No. 625,731

Claims.

This invention relates to cathode structures for electron-discharge devices, and while not limited thereto, it is especially suitable for use in electron-discharge devices of the magnetron type.

One of the disadvantages of existing cathode structures, which ordinarily consist of metallic cores provided with highly electron-emissive coatings, is the development, in the coatings, of hot spots. These hot spots are caused by the uneven thermal conductivity between the core and the coating, and result in rapid deterioration of the structure as an electron emitter.

It is, therefore, one of the objects of the present invention to provide a cathode structure having substantially uniform thermal conductivity throughout.

It is a further object of the present invention to provide a cathode structure in which there is improved coherence between the core and the coating thereof.

These, and other objects of the present invention, which will become more apparent as the detailed description thereof progresses, are attained, briefly, in the following manner:

In accordance with the present invention, a metallic base member is covered with a metallic gauze. A metallic cementing agent, dispersed in a suitable binder, is applied to the composite base member and gauze, which are then heated to a temperature suificient to drive off the binder and cause the cementing agent to sinter and bind the gauze to the base member. The resulting intimate contact between the gauze and the base member gives rise to substantially uniform, high thermal conductivity throughout. In addition, the gauze surface being porous, a subsequently applied electron-emissive coating fills the interstices thereof, thereby assuring greater coherence between the coating and the cathode core.

In the accompanying specification there shall be described, and in the annexed drawing shown, an illustrative embodiment of the electron-discharge device of the present invention. It is, however, to be clearly understood that the present invention is not to be limited to the details herein shown and described for purposes of illustration only, inasmuch as changes therein may be made without the exercise of invention, and within the true spirit and scope of the claims hereto appended.

In said drawing, the single figure is a longitudinal sectional view of a cathode structure made in accordance with the principles of the present invention.

Referring now more in detail to the aforesaid illustrative embodiment of the present invention, with particular reference to the drawing illustrating the same, the numeral I0 generally designates a cathode structure including a base member in the form of a metallic, preferably nickel, sleeve H. Said sleeve I l is surrounded by a metallic, preferably nickel, gauze [2 which, as herein shown in the drawing, has been greatly exagaerated.

In order to so bind the gauze to the sleeve as to assure good thermal conductivity therebetween throughout, a metallic cementing agent, for example, nickel powder, dispersed in a suitable binder, such as a nitro-cellulose amylacetate binder, is deposited, as by spraying, over the composite sleeve and gauze.

The whole is then heated, in a gaseous atmosphere adapted to prevent oxidation, for example, hydrogen, to a temperature sufficient to drive off the binder and cause the cementing agent to sinter, thereby fusing the gauze to the sleeve. The sintered cementing agent has been desig nated in the drawing by the reference character l3.

Thereafter, the structure is provided with any preferred electron-emissive coating M, for example, a mixture of barium and strontium carbonates dispersed in a suitable carrier. This coating may be sprayed onto the structure, and will flow into and fill the interstices of the auze The structure is completed by providing the same with a suitable heating filament I5.

This completes the description of the aforesaid illustrative embodiment of the present invention. It will be noted that the cathode structure of the present invention provides substantially uniform thermal conductivity between the electron-emissive coating and the cathode core, whereby the formation of hot spots is eliminated. It will further be noted that the porous character of the surface receiving the electron-emisslve coating provides improved coherence between said coating and the core.

Other objects and advantages of the present invention will readily occur to those skilled in the art to which the same relates.

What is claimed is:

l. A cathode structure comprising: a metallic core; a metallic gauze bound to said core by a fused metallic powder; and an electron-emissive coating deposited over said gauze.

2. A cathode structure comprising: a metallic core; a similarly metallic gauze bound to said core PERCY L. SPENCER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,075,122 Loewe et a1 Mar. 30, 1937 2,154,298 Ayer Apr. 11, 1939 2,251,410 Koehring et a1 Aug. 5, 1941 2,273,763 Rerink et a1 Feb. 17, 1942 2,359,361 Gleszer et a1 Oct. 3, 1944 FOREIGN PATENTS Number Country Date 108,740 Australia Oct. 8, 1937 

